1. Field of the Invention
The present invention relates to a method and apparatus for applying a protecting film to a semiconductor wafer, in which after a protecting film has been applied to the surface of a semiconductor wafer, the protecting film is cut to match the shape of the wafer.
2. Description of the Prior Art
When a semiconductor is manufactured, a grinding process (known as backgrinding) is carried out on the underside surface of the semiconductor wafer (hereafter referred to simply as "wafer") to thin it down in order to carry out miniaturization of the semiconductor chip, and in this process the upper surface (i.e., the surface formed with the circuit) is protected by the application of a protecting film made from a flexible film comprised of a base material such as an adhesive film or the like.
As for known methods of applying this protecting film, in one method the protecting film is applied after being precut to the same shape as the wafer, and in another method the protecting film is first applied to the wafer and then cut to match the shape of the wafer.
In this connection, in the method of the present invention described below, a tensile force (back tension) is applied along the feeding direction of the protecting film and along the opposite direction thereof in order to keep the protecting film in a stretched state so as to prevent wrinkles from forming, and in this state the protecting film is applied to the wafer.
However, in the above described prior art method, it is not possible to adjust the back tension. Consequently, when the back tension is too high, a shrinkage force will act on the applied film, and this creates such risks as warpage or rupturing.
Further, if the back tension is too low, wrinkles may form in the protecting film and air bubbles may enter between the protecting film and the wafer, thus creating the risk that such wafer cannot be used for the grinding process.
On the other hand, with regards to methods of applying the protecting film to the wafer and then cutting the protecting film to match the shape of the wafer, the prior art teaches a method in which such cutting is carried out by moving a cutter along the circumference of the wafer and another method in which the cutter is fixed and cutting is carried out by rotating the wafer.
For positioning of the semiconductor wafer, a straight line portion referred to as an orientation flat portion is formed, and in the prior art method of cutting the wafer protecting tape, the intersection of the orientation flat portion and the circumferential portion of the wafer forms an angular portion, and at this angular portion a remnant (burr) of the cut protecting tape is created.
When a cut remnant exists at this angular portion, such cut remnant can be pulled into the grinding apparatus during the backgrinding process, and if this occurs the entire semiconductor wafer can be destroyed. Consequently, up to now there has been a strong desire for a protecting film applying apparatus that does not leave behind such a cut remnant. Further, in the case where the bonding of the protecting film to the wafer is insufficient, such portion can also be pulled into the grinding apparatus and create the same problem described above, and this has lead to even more desire for improvement.